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C

D

?$-2a^2b^2+ab^3$?

?$3x^3-6x^2-3x$?

?$-a^3b^2+2a^2b^2$?

?$x $?

9

?$-\frac {5}{2}$?

?$2a(a+b)=2a^2+2ab $?

?$解：原式=3ab^2×2ab-2ab×ab$?

?$=3a^2b^3-2a^2b^2$?

解:原式?$=4a^2b^2(3a^2-2ab-4b^2)$?

?$=12a^4b^2-8a^3b^3-16a^2b^4$?

解:原式?$=-2a^2×\frac {1}{2}ab-2a^2b^2-5a^3b+5a^4b^2$?

?$=-a^3b-2a^2b^2-5a^3b+5a^4b^2$?

?$=-6a^3b+3a^2b^2$?

解:原式?$=-6 x^3 y+12 x^2 y^2+6 x y^3+6 x y^3 $?

?$=-6 x^3 y+12 x^2 y^2+12 x y^3$?

解?$：(1)$?根據(jù)題意, 得:

?$A^2C-B=(-2 x)^2(x-1) -(4 x^3-3 x^2-1) $?

?$=4 x^2(x-1)-4 x^3+3 x^2+1 $?

?$=4 x^3-4 x^2-4 x^3+3 x^2+1 $?

?$=-x^2+1 ；$?

?$(2)$?把?$ x=-\frac {1}{2} $?代入上式

?$ 則 A^2C-B=-x^2+1=-(-\frac {1}{2})^2+1 =-\frac {1}{4}+1 =\frac {3}{4} .$?

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